Conductive porous layer for batteries and fabrication method for same

Abstract

The conductive porous layer for batteries according to the present invention comprises a laminate comprising a first conductive layer and a second conductive layer. The first conductive layer includes at least a conductive carbon material and a polymer. The second conductive layer includes at least a conductive carbon material and a polymer. The conductive porous layer satisfies at least one of the following two conditions: “the polymer in the first conductive layer is present with a high density at the surface of the layer in contact with the second conductive layer than at the surface not in contact with the second conductive layer” and “the polymer in the second conductive layer is present with a higher density at the surface of the layer in contact with the first conductive layer than at the surface not in contact with the first conductive layer.”

The invention claimed is: 
     
       1. A method for producing the conductive porous layer for batteries comprising a laminate comprising a first conductive layer and a second conductive layer, the first conductive layer comprising at least a conductive carbon material and a polymer, and the second conductive layer comprising at least a conductive carbon material and a polymer, and the conductive porous layer satisfying at least one of the following conditions:
 (A) the polymer in the first conductive layer is present with a higher density at the surface of the layer in contact with the second conductive layer than at the surface not in contact with the second conductive layer, and 
 (B) the polymer in the second conductive layer is present with a higher density at the surface of the layer in contact with the first conductive layer than at the surface not in contact with the first conductive layer, the method comprising the steps of:
 (I) applying a first conductive layer-forming paste composition to a substrate and drying, wherein the composition comprises at least a conductive carbon material and a polymer, and then detaching the resulting first conductive layer from the substrate to produce a first conductive layer having a polymer with a higher density at one side surface than at the opposite side surface, 
 (II) applying a second conductive layer-forming paste composition to a substrate and drying, wherein the composition comprises at least a conductive carbon material and a polymer, and then detaching the resulting second conductive layer from the substrate to produce a second conductive layer having a polymer with a higher density at one side surface than at the opposite side surface, and 
 (III) disposing the first conductive layer and the second conductive layer in such a manner as to satisfy at least one of the following conditions:
 (A) the polymer in the first conductive layer is present with a higher density at the surface of the layer in contact with the second conductive layer than at the surface not in contact with the second conductive layer, and 
 (B) the polymer in the second conductive layer is present with a higher density at the surface of the layer in contact with the first conductive layer than at the surface not in contact with the first conductive layer; and performing hot-pressing for bonding. 
 
 
 
     
     
       2. The method according to  claim 1 , wherein the polymer in step (I) has a glass transition temperature of −100 to 300° C. 
     
     
       3. The method according to  claim 1 , wherein the polymer in step (II) has a glass transition temperature of −100 to 300° C. 
     
     
       4. The method according to  claim 1 , wherein step (III) is a step of disposing the first conductive layer and the second conductive layer in such a manner as to satisfy both of the conditions (A) and (B), and performing hot-pressing for bonding. 
     
     
       5. The method according to  claim 1 , wherein the conductive carbon material in step (II) is conductive carbon fibers with an average fiber diameter of 5 μm or more and/or conductive carbon particles with an average particle diameter of 5 μm or more.